The invention is based on a control device for an internal combustion engine operated with supercharging as generally defined hereinafter. A safety device for a supercharged internal combustion engine is already known in combination with a fuel metering system, in which the fuel metering is controlled in accordance with the volumetric efficiency of degree of charge of the engine (German Offenlegungsschrift No. 3026150 and U.S. Ser. No. 282,339). In the case of an excessively high degree of charge, a defect of the supercharger or its regulator is assumed. To protect the engine from mechanical or thermal overload, the fuel metering is reduced or shut off entirely in the case of such a defect.
One disadvantage of this known safety device is that a failure or malfunction in the devices used for measuring the degree of charge, such as an air flow sensor or an rpm meter, can cause an incorrect determination of the volumetric efficiency. The excessive charge which may possibly be effected as a result can destroy the engine in only a few seconds.
A method for the operation of and a device for a fuel metering system in an internal combustion engine during overrunning is also known (German Offenlegungsschrift No. 2801790 and U.S. Pat. No. 4,311,123). The method is distinguished by the provision that the fuel supply is reduced at the onset of overrunning and then shut off in accordance with an elective function. After the end of overrunning, the supply of fuel is resumed according to an elective function. This method includes characteristics for the control device according to the invention in the case of an engine operated with supercharging--such as the shutoff of the fuel supply--although the method per se is used only for braking the vehicle equipped with an internal combustion engine in the event of overrunning.